xfs: Introduce macros to represent new maximum extent counts for data/attr forks

This commit defines new macros to represent maximum extent counts allowed by
filesystems which have support for large per-inode extent counters.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index b317226..1254d4d 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -61,10 +61,8 @@ xfs_bmap_compute_maxlevels(
        int             sz;             /* root block size */
 
        /*
-        * The maximum number of extents in a file, hence the maximum number of
-        * leaf entries, is controlled by the size of the on-disk extent count,
-        * either a signed 32-bit number for the data fork, or a signed 16-bit
-        * number for the attr fork.
+        * The maximum number of extents in a fork, hence the maximum number of
+        * leaf entries, is controlled by the size of the on-disk extent count.
         *
         * Note that we can no longer assume that if we are in ATTR1 that the
         * fork offset of all the inodes will be
@@ -74,7 +72,8 @@ xfs_bmap_compute_maxlevels(
         * ATTR2 we have to assume the worst case scenario of a minimum size
         * available.
         */
-       maxleafents = xfs_iext_max_nextents(whichfork);
+       maxleafents = xfs_iext_max_nextents(xfs_has_large_extent_counts(mp),
+                               whichfork);
        if (whichfork == XFS_DATA_FORK)
                sz = XFS_BMDR_SPACE_CALC(MINDBTPTRS);
        else

diff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c
index 453309f..2b77d45 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap_btree.c
+++ b/fs/xfs/libxfs/xfs_bmap_btree.c
@@ -597,7 +597,11 @@ xfs_bmbt_maxrecs(
        return xfs_bmbt_block_maxrecs(blocklen, leaf);
 }
 
-/* Compute the max possible height for block mapping btrees. */
+/*
+ * Calculate the maximum possible height of the btree that the on-disk format
+ * supports. This is used for sizing structures large enough to support every
+ * possible configuration of a filesystem that might get mounted.
+ */
 unsigned int
 xfs_bmbt_maxlevels_ondisk(void)
 {
@@ -611,7 +615,8 @@ xfs_bmbt_maxlevels_ondisk(void)
        minrecs[1] = xfs_bmbt_block_maxrecs(blocklen, false) / 2;
 
        /* One extra level for the inode root. */
-       return xfs_btree_compute_maxlevels(minrecs, MAXEXTNUM) + 1;
+       return xfs_btree_compute_maxlevels(minrecs,
+                       XFS_MAX_EXTCNT_DATA_FORK_LARGE) + 1;
 }
 
 /*

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 57b2474..eb85bc9 100644 (file)
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -872,9 +872,29 @@ enum xfs_dinode_fmt {
 
 /*
  * Max values for extnum and aextnum.
+ *
+ * The original on-disk extent counts were held in signed fields, resulting in
+ * maximum extent counts of 2^31 and 2^15 for the data and attr forks
+ * respectively. Similarly the maximum extent length is limited to 2^21 blocks
+ * by the 21-bit wide blockcount field of a BMBT extent record.
+ *
+ * The newly introduced data fork extent counter can hold a 64-bit value,
+ * however the maximum number of extents in a file is also limited to 2^54
+ * extents by the 54-bit wide startoff field of a BMBT extent record.
+ *
+ * It is further limited by the maximum supported file size of 2^63
+ * *bytes*. This leads to a maximum extent count for maximally sized filesystem
+ * blocks (64kB) of:
+ *
+ * 2^63 bytes / 2^16 bytes per block = 2^47 blocks
+ *
+ * Rounding up 47 to the nearest multiple of bits-per-byte results in 48. Hence
+ * 2^48 was chosen as the maximum data fork extent count.
  */
-#define        MAXEXTNUM       ((xfs_extnum_t)0x7fffffff)      /* signed int */
-#define        MAXAEXTNUM      ((xfs_aextnum_t)0x7fff)         /* signed short */
+#define XFS_MAX_EXTCNT_DATA_FORK_LARGE ((xfs_extnum_t)((1ULL << 48) - 1))
+#define XFS_MAX_EXTCNT_ATTR_FORK_LARGE ((xfs_extnum_t)((1ULL << 32) - 1))
+#define XFS_MAX_EXTCNT_DATA_FORK_SMALL ((xfs_extnum_t)((1ULL << 31) - 1))
+#define XFS_MAX_EXTCNT_ATTR_FORK_SMALL ((xfs_extnum_t)((1ULL << 15) - 1))
 
 /*
  * Inode minimum and maximum sizes.

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index f0e0638..e0d3140 100644 (file)
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -361,7 +361,9 @@ xfs_dinode_verify_fork(
                        return __this_address;
                break;
        case XFS_DINODE_FMT_BTREE:
-               max_extents = xfs_iext_max_nextents(whichfork);
+               max_extents = xfs_iext_max_nextents(
+                                       xfs_dinode_has_large_extent_counts(dip),
+                                       whichfork);
                if (di_nextents > max_extents)
                        return __this_address;
                break;

diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index 004b205..bb5d841 100644 (file)
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -744,7 +744,8 @@ xfs_iext_count_may_overflow(
        if (whichfork == XFS_COW_FORK)
                return 0;
 
-       max_exts = xfs_iext_max_nextents(whichfork);
+       max_exts = xfs_iext_max_nextents(xfs_inode_has_large_extent_counts(ip),
+                               whichfork);
 
        if (XFS_TEST_ERROR(false, ip->i_mount, XFS_ERRTAG_REDUCE_MAX_IEXTENTS))
                max_exts = 10;

diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 4a8b77d..967837a 100644 (file)
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -133,12 +133,25 @@ static inline int8_t xfs_ifork_format(struct xfs_ifork *ifp)
        return ifp->if_format;
 }
 
-static inline xfs_extnum_t xfs_iext_max_nextents(int whichfork)
+static inline xfs_extnum_t xfs_iext_max_nextents(bool has_large_extent_counts,
+                               int whichfork)
 {
-       if (whichfork == XFS_DATA_FORK || whichfork == XFS_COW_FORK)
-               return MAXEXTNUM;
+       switch (whichfork) {
+       case XFS_DATA_FORK:
+       case XFS_COW_FORK:
+               if (has_large_extent_counts)
+                       return XFS_MAX_EXTCNT_DATA_FORK_LARGE;
+               return XFS_MAX_EXTCNT_DATA_FORK_SMALL;
+
+       case XFS_ATTR_FORK:
+               if (has_large_extent_counts)
+                       return XFS_MAX_EXTCNT_ATTR_FORK_LARGE;
+               return XFS_MAX_EXTCNT_ATTR_FORK_SMALL;
 
-       return MAXAEXTNUM;
+       default:
+               ASSERT(0);
+               return 0;
+       }
 }
 
 static inline xfs_extnum_t